PERTURBATION OF PLATELET-ADHESION TO ENDOTHELIAL-CELLS BY PLASMINOGENACTIVATION IN-VITRO

To investigate whether the endothelium-platelet interactions may be al tered by plasminogen activation, cultured human umbilical vein endothe lial cells (ECs) were treated with tissue-type plasminogen activator ( t-PA) in the presence of plasminogen, and platelet adhesion to ECs was subsequently measured by using a tapered flow chamber. Our results de monstrated that platelets adhered more readily to t-PA treated EC mono layer than to the control monolayer at all shear stress levels tested. This phenomenon was treatment time-dependent and dose-dependent. and it could be blocked by adding plasmin inhibitors. such as epsilon-amin o caproic acid and aprotinin. Adherent platelets on t-PA treated EC mo nolayer underwent more severe shape change than those on the control m onolayer. While the extracellular matrix directly treated with t-PA at tracted less platelets than the control matrix did, platelet adhesion to the matrix that was produced by t-PA-treated ECs was unaltered. The se data suggest that t-PA treatment on ECs compromised antiplatelet-ad hesion capability on their apical surface without altering the reactiv ity of their extracellular matrix towards platelets.